Modern shotgun shells (frequently referred to as shotshells) are made up of five basic components: a case (the overall packaging), a primer, powder, a wad (or wad column) and shot. The case is made up of brass (otherwise referred to as the "head" of the shotshell), a base wad, and a tube or wall. The primer is seated in the primer pocket. Powder is poured into the tube on top of the base wad and a plastic wad is pressed down on top of the powder within the tube. The shot charge is then poured into the wad cup. Finally, the top of the shell tube is creased and crimped down tightly on top of the shot charge by the machinery loading the shot shells.
To fire the shotgun, a loaded shotshell is placed in the chamber. The trigger is pulled and the firing pin strikes the primer in the shotshell. The primer detonates, igniting the powder charge. The rapidly expanding gases generated by the explosion of the powder charge strike the wad with its load of shot in the shot cup with a blow equal to approximately 12,000 pounds per square inch. The wad, being lighter than the shot, is driven forward into the column of shot nestled in the shot cup.
At this point, undesirable things happen when known wads are being used. The shot charge is, in effect, driven into the floor and the immediately adjacent sides of the shot cup with tremendous force. When the shell is loaded with lead shot, the whole band of shot at the back of the shot column becomes deformed either by contact with other shot or with the steel sides of the chamber of the shotgun barrel. Upon eventually exiting the barrel, these deformed shot fly off (hence the name "flyers") at strange angles, none of which is in the direction of the target. With steel shot, the deformation of pellets is greatly reduced, but still occurs. Perhaps more important is the fact that the steel pellets at the back of the shot column, in effect, beat on the walls of the chamber of the barrel like dozens of ballpeen hammers, a situation that could cause a flawed barrel, or one that has simply been worn out by repeated blows. A further problem is that when the shot cup is driven into the shot column, the recoil force is transferred to the shoulder of the shooter. Because, in known wad designs, the shot cup floor hits the shot column with a tremendous force, the recoil felt by the shooter is a sudden, sharp blow.
The shot exits the chamber into what is known as the forcing cone. This is a section of barrel that tapers from the diameter of the chamber down to the effective diameter of the barrel for most of its length. At this point, more undesirable things happen when known wads are being used. The shot charge stretches out and some of the shot escapes from the wad cup. As this occurs, much of the escaped shot can come in direct contact with the inside of the barrel, causing wear on the barrel with both types of shot, and coating the interior of the barrel with lead when lead shot is used. Another problem with the shot directly contacting the inside of the barrel is that friction is generated between the shot and the barrel, which in turn causes the shot to lose velocity. The same sequence of events occur as the wad and shot charge approach the muzzle of the barrel where they are again constricted, this time by the choke at the muzzle, which is intended to regulate the size of the pattern the shot achieves upon leaving the barrel.
Now the wad and the shot charge exit the barrel. At this point it is important to rapidly separate the shot charge from the wad, so that the wad cannot interfere with the shot pattern. Not only must the wad be quickly slowed, but it must be done so in a manner such that the wad does not spin out of control, interfering with shot proximate to, or even still contained within, the wad. Known designs do not adequately achieve this. The wad often travels up to forty yards downrange, which is approximately two-thirds of the expected range of the shot. Moreover, known wads can deliver only approximately two-thirds of the shot charge on target in a useful pattern.
What is desired, therefore, is a shotshell wad which results in few flyers, which reduces damage to the chamber of the barrel upon firing, which reduces the recoil felt by the shooter upon firing, which inhibits the shot from escaping the shot cup and directly contacting the inside of the barrel, which is quickly separated from the shot upon exiting the barrel, and which delivers the shot charge on target in a useful pattern.